Patent Literature 1 proposes a technique which estimates the physical quantity of an object from a captured image by a particle filter method and estimates the position of an object by a condensation method by taking a quantity related to the feature quantity of the object as a weight.
Patent Literature 2 proposes a technique in which a three-dimensional model comprised of a plurality of feature points with three-dimensional coordinate values and partial image data representing a partial image related to each feature point is projected into a two-dimensional observation space, the state quantity of the three-dimensional model is estimated using a feature point set selected in the two-dimensional observation space, the estimated three-dimensional model state is projected into the observation space and the adaptability is repeatedly calculated to estimate the state quantity of the three-dimensional model.
In Patent Literature 3, an area of interest for determining the presence of a target is sequentially set in a plurality of positions in an image, a reference position of a part is set according to a deformable part model (spring model) when it is assumed that a target is present in the area of interest, and a deformation cost as a value representing the degree of deviation from the reference position is calculated for each of detected parts. Then a technique is proposed in which, on the condition that a plurality of parts in the same kind whose calculated deformation costs are within a prescribed range are present, the area of interest is decided to be a target area where a target constituting a group is present.